Treatment of edible oils



United States Patent TREATMENT OF EDIBLE OILS Alan Roylance, Bebington, Stanley Paul, Prenton, Birkenhead, and Reginald James Taylor, I-leswall, England, assignors to Lever Brothers Company, New York, N.Y., a corporation of Maine No Drawing. Filed Mar. 19, 1958, Ser. No. 722,401 Claims priority, application Great Britain Mar. 21, 1957 15 Claims. (Cl. 99-163) This invention relates to glyceride oils and especially to a process for treating glyceride oils for edible purposes to improve their storage properties.

A difliculty sometimes experienced on storage of edible glyceride Oils is the development of off flavours which are diflicult to describe and vary in nature from one oil to another but which are readily distinguishable from the flavours associated with oxidative rancidity. Some edible oils for instance develop an off flavour that has been termed beany, in others a paint-like off flavour is encountered. The chemical reactions leading to this flavour deterioration are not understood. The usual methods of refinement practiced in preparing edible glyceride oils, which comprise subjecting the oil successively to alkali refining (in which free acidis neutralised), bleaching with activated fullers earth and steam deodorisation, do not prevent the early onset of this form of flavour deterioration. Nor has the addition of antioxidants been found beneficial in reducing the rate of this deterioration. It has now been found however that a valuable reduction in the rate of flavour deterioration can be obtained by first treating the oil, in solution in a non-polar solvent, with activated alumina and subsequently (for instance after the steam-deodorisation) adding an antioxidant.

Treatment according to the invention, therefore, which is preferably applied immediately after the alkali refining step, comprises contacting the oil, in solution in a nonpolar solvent, with activated alumina and subsequently removing the solvent, applying a steam-deodorising treatment and adding a suitable antioxidant.

As indicated above, in the preparation of edible oils according to the invention the inclusion of a bleaching step such as the normal treatment with activated fullers earth is preferably avoided. It has been found that oils which have been given such a bleaching treatment before treatment with the alumina do not always remain palatable for as long as if the bleaching treatment had been omitted.

To obtain the best results the antioxidant should be present in the final product. The oil to which the antioxidant has been added should not therefore be further processed in such a way as to destroy the antioxidant. It is best added immediately after, or towards the end of, the deodorising treatment. H I l v The nature and amount of antioxidant employed must of course be such that the oil is not rendered unpalatable or injurious to health by the presence of the antioxidant or of any reaction product that may be formed from it during storage of the oil containing it. Suitable antioxidants are alkyl esters of hydroxy benzoic acids, especially gallic acid, for instance p'ropyl, octyl and dodecyl gallates, and alkyl phenols such as tertiary alkyl nuclear substitution derivatives of hydroxy alkoxy benzenes, especially anisole, for instance 2-tert.-butyl-4- hydroxy anisole and 3-tert.-butyl-4-hydroxy anisole (commercial butylated anisole is a mixture of these isomers) and trialkyl nuclear substitution derivatives of phenol, for instance 2-6-di-tert. butyl-4-methyl phenol (commonly termed butylated hydroxy toluene).

It is of advantage to add with the antioxidant a small proportion, for instance the same weight as the antioxidant, of citric acid.

Suitable non-polar solvents include petroleum fractions hexane and cyclohexane. The proportion of solvent to oil should be neither so low that the solution is too viscous to be readily treated with and separated from the alumina, nor so .high that the subsequent removal of solvent from the oil makes the process unnecessarily costly. Normally the oil-content of the solution will be between 5 and 50% weight/volume, preferably between 25 and 40% weight/volume, the weight being expressed in grammes and volume in millilitres. After treatment of the solution, the alumina may be washed with a further quantity of the solvent to remove occluded oil.

The activated alumina is produced by heating an alumina hydrate. Alumina trihydrate, for instance in the form of gibbsite or bayerite is very suitable, the form known as gibbsite being preferred. Gibbsite for instance, may be activated by heating between 350 and 900 C., and preferably between 350 and 500 C., for instance for 5 hours or more. The proportion of alumina to oil may vary within wide limits, depending particularly on the oil being treated and the degree of stabilisation required. Normally, suitable proportions of alumina will fall within the range of 5-500% by weight of the oil, and most frequently within the range of 25-250% by weight of the oil.

A convenient method of contacting alumina and solution is to pass the latter down a column of the alumina, but the process may be carried out by agitating together a mixture of alumina and the solution of the oil. For economic reasons, the process will normally be carried out as near to room temperature as possible. For more concentrated solutions of solid fats, it may be necessary to usea raised temperature to prevent deposition of solid fat from the solution.

After the alumina treatment, solvent is removed, preferably by distillation, and the oil deodorised by blowing steam through it, for instance, at l40-180 C. under reduced pressure. This deodorisation also serves to remove the last traces of solvent from the oil.

The process of the invention is of most importance in preparing refined preferably unhardened edible vegetable oils. Examples of oils that may be treated with advantage according to the invention are: cottonseed, olive,ground nut, sesame, sunflower, satflower, soya bean and rape seed oils. 1

The following examples illustrate the process of the invention:

' Example 1 300 g. of groundnut oil neutralised by an alkali refining step was dissolved in light petrol (B. Pt. 40-60 C.) so as to give a 25% weight/volume solution and this solution was passed down a column 40 cms. long filled with 500 g. of activated alumina which had been made by heating gibbsite at 400 C. for 7 hours. After pas: sage of the solution, the column was washed with 1800 mls. of light petrol and the oil recovered from the com bined eluates by distilling oif the petrol. The recovered oil was deodorised at 180 C. for 3 hours at a pressure of l-2 mm. Hg. Finally, 0.01% of butylated hydroxy anisole was dissolved in the freshly deodorised oil; this was effected by stirring the calculated quantity of antioxidant with a small portion of the oil at 40 C., the solution thus formed being then returned to the main bulk of the oil.

This oil was found to be free from objectionable flavours after storage at room temperature with access to Example 2 The process was carried out as in Example 1 except that for the butylated hydroxy anisole the same weight of propyl gallate was substituted.

Example 3 The process was carried out as in Example 1 except that for the butylated hydroxy anisole the same weight of butylated hydroxy toluene was substituted.

Example 4 400 g. of neutralised groundnut oil in 600 ml. of petrol ether (B. Pt. 40-60 C.) was passed down a colmum of alumina cm. in height and containing 100 g. of alumina activated at 400600 C. for 21 hours. The column was washed with 600 ml. of petrol ether and the combined eluates evaporated. The alumina-treated oil was steam-deodorised at 180 C. for three hours, 0.4 g. of an antioxidant mixture, consisting of a solution of 0.08 g. of butylated hydroxy anisole, 0.016 g. of citric acid and 0.024 g. of propyl gallate in 0.28 g. of propyl ene glycol, was added to the deodorised oil. The oil remained of good quality for 8 weeks.

Example 5 250 g. of neutralised soyabean oil was dissolved in 750 ml. of light petrol (B. Pt. -60 C.), and this solution was passed down a column 3.5 crns. in diameter filled with 500 g. of alumina activated by heating the trihydrate at 400-600 C. for 21 hours. After passage of the solution the column was washed with 1500 ml. of the petrol. The oil was recovered from the combined eluate by distilling off the petrol under nitrogen. 4 ml. of a 1% solution of citric acid were added to the oil which was then steam-deodorised at 180 C. for 3 hours at a pressure of 1-2 mm. of Hg, 2. further 4 ml. of the citric acid solution being added /2 hour before the end of the deodorisation. Finally 0.02% of hutylated hydroxy anisole was dissolved in the freshly deodorised oil.

A sample of the same neutralised soyabean oil was processed by conventional means and 0.02% of butylated hydroxy anisole was also added.

Both samples of oil were stored at room temperature for six weeks. At this time the oil treated with alumina was of good edible quality whereas the bleached oil possessed a strong objectionable flavour.

Example 6 solution of citric acid were added and the oil was steamdeodorised for 3 hours at C. A bleached and deodorised oil was also prepared, and 0.02% of butylated hydroxy anisole was added to each sample. The alumina-treated oil remained of markedly better edible quality on storage than. the bleached sample.

We claim:

1. A process for preparing a refined edible vegetable glyceride oil of improved keeping qualities which comprises dissolving a neutralized edible vegetable oil in a non-polar solvent, contacting the solution thus obtained with activated alumina, removing the solvent from the oil, steam-deodorizing the oil and adding an antioxidant to the oil, said antioxidant being added to the oil not substantially later than the end of the deodorizing step.

2. A process according to claim 1, wherein the oil is treated in the unbleached condition.

3. A process according to claim 1, wherein the oil is contacted with the activated alumina by causing the solution of the oil to pass through a column containing the flumina.

4. A process according to claim 1, wherein the oil treated is unhardened groundnut oil.

5. A process according to claim 1, wherein the oil treated is unhardened soyabean oil.

6. A process according to claim 1, wherein the oil treated is unhardened rapeseed oil.

7. A process according to claim 1, wherein the antioxidant is an alkyl ester of gallic acid.

8. A process according to claim 1, wherein the antioxidant is a tert.-alkyl nuclear substitution derivative of a hydroxy anisole.

9. A process according to claim 1, wherein the antioxidant is 2,6-di-tert.-butyl-4-methyl phenol.

10. A process according to claim 1, wherein the oil treated is neutralized unbleached groundnut oil and the antioxidant is propyl gallate.

11. A process according to claim 1, wherein the oil treated is neutralized unbleached groundnut oil and the antioxidant is a mixture of 2-tert.-butyl-4-hydroxy anisole and 3-tert.-butyl-4-hydroxy anisole.

12. A process according to claim 1, wherein the oil treated is neutralized groundnut oil and the antioxidant is 2,6-di-tert.-butyl-4-methyl phenol.

13. A process according to claim 1, wherein the oil treated is neutralized unbleached soyabean oil and the antioxidant is a mixture of 2-tert.-butyl-4-hydroxy anisole and 3-tert.-butyl-4-hydroxy anisole.

14. A process according to claim 1, wherein the oil treated is neutralized unbleached rapeseed and the antioxidant is a mixture of 2-tert.-butyl-4'hydroxy anisolc and 3-tert.-butyl-4-hydroxy anisole.

15. A process according to claim 1, wherein there is added with the antioxidant a small proportion of citric acid.

References Cited in the file of this patent UNITED STATES PATENTS 2,272,964 Coe et al. Feb. 10, 1942 2,454,937 Moyer et al. Nov. 30, 1948 2,607,745 Magoffin Aug. 19, 1952 2,677,616 Hall May 4, 1954 2,726,159 Newby et al. Dec. 6, 1955 

1. A PROCESS FOR PREPARING A REFINED EDIBLE VEGETABLE GLYCERIDE OIL OF IMPROVED KEEPING QUALITIES WHICH COMPRISES DISSOLVING A NEUTRALIZED EDIBLE VEGETABLE OIL IN A NON-POLAR SOLVENT, CONTACTING THE SOLUTION THUS OBTAINED WITH ACTIVATED ALUMINA, REMOVING THE SOLVENT FROM THE OIL, STEAM-DEODORIZING THE OIL AND ADDING AN ANTIOXIDANT TO THE OIL, SAID ANTIOXIDANT BEING ADDED TO THE OIL NOT SUBSTANTIALLY LATER THAN THE END OF THE DEODORIZING STEP. 